Optionally even widths of `display-buffer' windows. (Bug#21100)
* lisp/window.el (quit-restore-window): Restore width if
requested.
(display-buffer-record-window): Record width when window is
reused and horizontally combined.
(even-window-sizes): New option to allow evening window widths.
(even-window-heights): Defalias to `even-window-sizes'.
(window--even-window-heights): Rename to
`window--even-window-sizes'. Handle side-by-side windows.
(display-buffer-use-some-window): Call `window--even-window-sizes'
instead of `window--even-window-heights'.
* lisp/help.el (resize-temp-buffer-window): Fix indentation.